You shoud think twice before feeding your pet a chocolate bar. The sweet treat could be its last meal.

Chocolate contains theobromine, a compound that is a strong chemical stimulant. In humans, who metabolize the alkaloid quickly, theobromine has been shown to have some beneficial effects including mood elevation, myocardial stimulation, cough surpression, and vasodilation (widening of blood vessels from relaxation of the muscular wall of the vessels).

However animals — especially cats, dogs, horses, birds, and small pets — are unable to effectively metabolize theobromine. If they are fed chocolate, theobromine will remain in their bloodstream for up to 20 hours and may cause epileptic seizures, internal bleeding, heart attacks, and even death. Chocolate is such a potent stimulant than it is banned in horse-racing as a performance-enhancing drug.

According to The Merck Veterinary Manual, 8th Edition Online, “clinical signs of toxicity can occur with ingestion of ~0.04 oz (1.3 mg) of baker’s chocolate or 0.4 oz (13 mg) of milk chocolate per kilogram of body weight.” This means that a one-ounce (28 gram) square of baker’s chocolate would cause symtoms in a 50-pound (22 kilogram) dog.

The Merck Veterinary Manual puts a lethal dose (for 50% of the canine population) at 250 and 500 mg of theobromine per kg of body weight but warns that deaths have been reported at dosages as low as 115 mg/kg. Thus were a 45 pound (20 kg) dog to eat 7.5 pounds (3.3 kg) of dark chocolate, it would only have a 50% chance of survival. Granted, that’s a lot of chocolate but remember that for some dogs a lethal dose could be only half that amount. Dark chocolate generally contains about 50% more theobromine than milk chocolate.

Below are some sample estimates for selected breeds of dogs. Bear in mind that these are only estimates based on average weights for a breed. Some breeds may have higher or lower tolerances than others and toxicity varies between individuals.

Amount of Dark Chocolate causing

Average

Intestinal

Bradycardia or

50% probability

Breed

Weight

problems

Tachyarrythmia

of death

Afghan

60 lbs (27 kg)

7.4 oz (210 g)

15.4 oz (437 g)

154.4 oz (4,371 g)

American Cocker Spaniel

26 lbs (12 kg)

3.2 oz (91 g)

6.7 oz (189 g)

66.9 oz (1,894 g)

Basset Hound

45 lbs (20 kg)

5.6 oz (158 g)

11.6 oz (328 g)

115.8 oz (3,278 g)

Beagle

26 lbs (12 kg)

3.2 oz (91 g)

6.7 oz (189 g)

66.9 oz (1,894 g)

Bloodhound

90 lbs (41 kg)

11.1 oz (315 g)

23.2 oz (656 g)

231.7 oz (6,556 g)

Border Collie

45 lbs (20 kg)

5.6 oz (158 g)

11.6 oz (328 g)

115.8 oz (3,278 g)

Borzoi

90 lbs (41 kg)

11.1 oz (315 g)

23.2 oz (656 g)

231.7 oz (6,556 g)

Boxer

70 lbs (32 kg)

8.7 oz (245 g)

18.0 oz (510 g)

180.2 oz (5,099 g)

Bulldog

50 lbs (23 kg)

6.2 oz (175 g)

12.9 oz (364 g)

128.7 oz (3,642 g)

Bulldog – American

85 lbs (39 kg)

10.5 oz (298 g)

21.9 oz (619 g)

218.8 oz (6,192 g)

Bullmastiff

127 lbs (58 kg)

15.7 oz (445 g)

32.7 oz (925 g)

326.9 oz (9,252 g)

Chihuahua

4 lbs (2 kg)

0.5 oz (14 g)

1.0 oz (29 g)

10.3 oz (291 g)

Collie

67 lbs (30 kg)

8.3 oz (235 g)

17.2 oz (488 g)

172.5 oz (4,881 g)

Dachshund (Standard)

15 lbs (7 kg)

1.9 oz (53 g)

3.9 oz (109 g)

38.6 oz (1,093 g)

Dalmatian

60 lbs (27 kg)

7.4 oz (210 g)

15.4 oz (437 g)

154.4 oz (4,371 g)

Doberman Pinscher

75 lbs (34 kg)

9.3 oz (263 g)

19.3 oz (546 g)

193.1 oz (5,464 g)

English Cocker Spaniel

31 lbs (14 kg)

3.8 oz (109 g)

8.0 oz (226 g)

79.8 oz (2,258 g)

English Setter

67 lbs (30 kg)

8.3 oz (235 g)

17.2 oz (488 g)

172.5 oz (4,881 g)

Foxhound – American

73 lbs (33 kg)

9.0 oz (256 g)

18.8 oz (532 g)

187.9 oz (5,318 g)

Golden Retriever

70 lbs (32 kg)

8.7 oz (245 g)

18.0 oz (510 g)

180.2 oz (5,099 g)

Great Dane

140 lbs (64 kg)

17.3 oz (490 g)

36.0 oz (1,020 g)

360.4 oz (10,199 g)

Greyhound

67 lbs (30 kg)

8.3 oz (235 g)

17.2 oz (488 g)

172.5 oz (4,881 g)

Irish Setter

70 lbs (32 kg)

8.7 oz (245 g)

18.0 oz (510 g)

180.2 oz (5,099 g)

Jack Russell Terrier

15 lbs (7 kg)

1.9 oz (53 g)

3.9 oz (109 g)

38.6 oz (1,093 g)

Labrador Retriever

73 lbs (33 kg)

9.0 oz (256 g)

18.8 oz (532 g)

187.9 oz (5,318 g)

Maltese

7 lbs (3 kg)

0.9 oz (25 g)

1.8 oz (51 g)

18.0 oz (510 g)

Mastiff

200 lbs (91 kg)

24.8 oz (700 g)

51.5 oz (1,457 g)

514.8 oz (14,569 g)

Pointer

65 lbs (30 kg)

8.0 oz (228 g)

16.7 oz (474 g)

167.3 oz (4,735 g)

Poodle (Toy)

8 lbs (4 kg)

1.0 oz (28 g)

2.1 oz (58 g)

20.6 oz (583 g)

Pug

16 lbs (7 kg)

2.0 oz (56 g)

4.1 oz (117 g)

41.2 oz (1,166 g)

Rhodesian Ridgeback

85 lbs (39 kg)

10.5 oz (298 g)

21.9 oz (619 g)

218.8 oz (6,192 g)

Rottweiler

112 lbs (51 kg)

13.9 oz (392 g)

28.8 oz (816 g)

288.3 oz (8,159 g)

Saint Bernard

150 lbs (68 kg)

18.6 oz (525 g)

38.6 oz (1,093 g)

386.1 oz (10,927 g)

Schnauzer (Standard)

40 lbs (18 kg)

5.0 oz (140 g)

10.3 oz (291 g)

103.0 oz (2,914 g)

Shih Tzu

12 lbs (5 kg)

1.5 oz (42 g)

3.1 oz (87 g)

30.9 oz (874 g)

Siberian Husky

53 lbs (24 kg)

6.6 oz (186 g)

13.6 oz (386 g)

136.4 oz (3,861 g)

Yorkshire

6 lbs (3 kg)

0.7 oz (21 g)

1.5 oz (44 g)

15.4 oz (437 g)

Amount of Milk Chocolate causing

Average

Intestinal

Bradycardia or

50% probability

Breed

Weight

problems

Tachyarrythmia

of death

Afghan

60 lbs (27 kg)

11.1 oz (314 g)

23.1 oz (652 g)

230.5 oz (6,524 g)

American Cocker Spaniel

26 lbs (12 kg)

4.8 oz (136 g)

10.0 oz (283 g)

99.9 oz (2,827 g)

Basset Hound

45 lbs (20 kg)

8.3 oz (235 g)

17.3 oz (489 g)

172.9 oz (4,893 g)

Beagle

26 lbs (12 kg)

4.8 oz (136 g)

10.0 oz (283 g)

99.9 oz (2,827 g)

Bloodhound

90 lbs (41 kg)

16.6 oz (470 g)

34.6 oz (979 g)

345.8 oz (9,785 g)

Border Collie

45 lbs (20 kg)

8.3 oz (235 g)

17.3 oz (489 g)

172.9 oz (4,893 g)

Borzoi

90 lbs (41 kg)

16.6 oz (470 g)

34.6 oz (979 g)

345.8 oz (9,785 g)

Boxer

70 lbs (32 kg)

12.9 oz (366 g)

26.9 oz (761 g)

268.9 oz (7,611 g)

Bulldog

50 lbs (23 kg)

9.2 oz (261 g)

19.2 oz (544 g)

192.1 oz (5,436 g)

Bulldog – American

85 lbs (39 kg)

15.7 oz (444 g)

32.7 oz (924 g)

326.6 oz (9,242 g)

Bullmastiff

127 lbs (58 kg)

23.5 oz (664 g)

48.8 oz (1,381 g)

487.9 oz (13,808 g)

Chihuahua

4 lbs (2 kg)

0.7 oz (21 g)

1.5 oz (43 g)

15.4 oz (435 g)

Collie

67 lbs (30 kg)

12.4 oz (350 g)

25.7 oz (728 g)

257.4 oz (7,285 g)

Dachshund (Standard)

15 lbs (7 kg)

2.8 oz (78 g)

5.8 oz (163 g)

57.6 oz (1,631 g)

Dalmatian

60 lbs (27 kg)

11.1 oz (314 g)

23.1 oz (652 g)

230.5 oz (6,524 g)

Doberman Pinscher

75 lbs (34 kg)

13.9 oz (392 g)

28.8 oz (815 g)

288.1 oz (8,155 g)

English Cocker Spaniel

31 lbs (14 kg)

5.7 oz (162 g)

11.9 oz (337 g)

119.1 oz (3,371 g)

English Setter

67 lbs (30 kg)

12.4 oz (350 g)

25.7 oz (728 g)

257.4 oz (7,285 g)

Foxhound – American

73 lbs (33 kg)

13.5 oz (382 g)

28.0 oz (794 g)

280.5 oz (7,937 g)

Golden Retriever

70 lbs (32 kg)

12.9 oz (366 g)

26.9 oz (761 g)

268.9 oz (7,611 g)

Great Dane

140 lbs (64 kg)

25.9 oz (732 g)

53.8 oz (1,522 g)

537.9 oz (15,222 g)

Greyhound

67 lbs (30 kg)

12.4 oz (350 g)

25.7 oz (728 g)

257.4 oz (7,285 g)

Irish Setter

70 lbs (32 kg)

12.9 oz (366 g)

26.9 oz (761 g)

268.9 oz (7,611 g)

Jack Russell Terrier

15 lbs (7 kg)

2.8 oz (78 g)

5.8 oz (163 g)

57.6 oz (1,631 g)

Labrador Retriever

73 lbs (33 kg)

13.5 oz (382 g)

28.0 oz (794 g)

280.5 oz (7,937 g)

Maltese

7 lbs (3 kg)

1.3 oz (37 g)

2.7 oz (76 g)

26.9 oz (761 g)

Mastiff

200 lbs (91 kg)

36.9 oz (1,045 g)

76.8 oz (2,175 g)

768.4 oz (21,745 g)

Pointer

65 lbs (30 kg)

12.0 oz (340 g)

25.0 oz (707 g)

249.7 oz (7,067 g)

Poodle (Toy)

8 lbs (4 kg)

1.5 oz (42 g)

3.1 oz (87 g)

30.7 oz (870 g)

Pug

16 lbs (7 kg)

3.0 oz (84 g)

6.1 oz (174 g)

61.5 oz (1,740 g)

Rhodesian Ridgeback

85 lbs (39 kg)

15.7 oz (444 g)

32.7 oz (924 g)

326.6 oz (9,242 g)

Rottweiler

112 lbs (51 kg)

20.7 oz (585 g)

43.0 oz (1,218 g)

430.3 oz (12,177 g)

Saint Bernard

150 lbs (68 kg)

27.7 oz (784 g)

57.6 oz (1,631 g)

576.3 oz (16,309 g)

Schnauzer (Standard)

40 lbs (18 kg)

7.4 oz (209 g)

15.4 oz (435 g)

153.7 oz (4,349 g)

Shih Tzu

12 lbs (5 kg)

2.2 oz (63 g)

4.6 oz (130 g)

46.1 oz (1,305 g)

Siberian Husky

53 lbs (24 kg)

9.8 oz (277 g)

20.4 oz (576 g)

203.6 oz (5,763 g)

Yorkshire

6 lbs (3 kg)

1.1 oz (31 g)

2.3 oz (65 g)

23.1 oz (652 g)

According to The Merck Veterinary Manual, in dogs, early clinical signs of recent chocolate ingestion “usually include excitement, agitation or nervousness, increased thirst, and vomiting. In acute cases, signs most commonly develop within 12 hr. Hyperactivity, ataxia, diarrhea, or a diuresis may also be noted. Severely affected animals may have clonic muscle spasms, hyperthermia, and clonic seizures that may progress to coma. Infrequently, animals with minimal clinical signs may die suddenly, presumably due to fatal cardiac arrhythmias.”

If your pet does ingest chocolate you should induce vomiting or take the animal directly to the vet.

Chocolate is meant for humans, not animals. Never feed your pet any amount of chocolate.

This article used information and text from The Merck Veterinary Manual, 8th Edition Online and Wikipedia.